Recovery of naphthoquinone from crude product containing phthalic anhydride and naphthalene



QUINONE FROM CRUDE PRODUCT J. M. SAYWARD Filed NOV, 3, 1953 Feb. 26, 1957 RECOVERY OF' NAPHTH CONTAINING PHTHALIC ANHYDRIDE AND NAPHTHALENE Pika-nv r 2 of; af/VQ //v ,4m/fo aspx/45E ffm/nen ruff :600e INVENToR daf/N Maw/fw mmm/Pp BY `7 f( @Vm ATTORNEY nite Y 2,7S3,251 RECOVERY F NAPHTHQUNONE FROM VCRUDE PRODUCT vCNTAINING PHTHAL- IC ANHYDRIDE AND NAPHTHLENE John Mayhew Sayward, Springdale, Conn., assigner to American Cyanarnid Company, New York, N. Y., a corporation of Maine naphthoquinone from crude mixtures comprising phthalic anhydride and/ or phthalic acid and naphthoquinone.

ln the preparation or naphthoquinone by the controlled v catalytic Aoxidation of naphthalene vapors with air, n'aphlthoquinone is formed as one of the products ofthe reaction, along with other compounds, such as, for example, phthalic anhydride. Additionally, some unreacted naphthalene is present in varying quantities in the crude reaction mixture. For example, using a suitable catalyst and operating conditions such as would be employed in industry, a yield Vof approximately 2O to 35 lbs. of naphthoquinone per l0() lbs. of naphthalene has been obtained, as well as from about l to 3 times that amount of phthalicanhydride, and from 0.2 to about 1.5 times that amount or' unchanged naphthalene. are merely typical and illustrative yand are not toy be considered as limitative `of the possible yields; in fact, yields of up to 45-'50 lbs. of naphthoquinone per 100 lbs. of naphthalene have been obtained.

Several method for recovering the naphthoquinone Afrom crude mixtures Vcontaining phtna'lic anhydride and/ or acid and naphthoquinone have been hitherto proposed in the industry. According to one method, the mixture is yextracted with a solvent, such as kbenzenain which the naphthoquinone is soluble but in which the phthalic acid is insoluble. This method is ineficient and Ydangerous due to the use of the expensive kand iiammable solvent S l l uci va lues)30 rates i atentf fi,ic

yor semi-continuous batch operation.

Still another object of the present invention is to provide a process of recovering naphthoquinone without deteriorating the same and in a suiciently pure form to permit its use in commercial processes.

Other objects, as well as benefits and advantages of Ythe invention will be apparent from the lfollowing description andaccompanying drawings, wherein:

Fig. l shows the loss of naphthoquinone to the aqueous phthalic acid phase due to varying water usage; and

Fig. 2 -shows the phase relationship in the naphthoquinone-naphthalene phase for varying temperatures.

l have discovered a simple means of recovering highgrade, substantially pure naphthoquinone from a crude solid mixture of naphthoquinone, naphthalene and phthalic anhydride, such as may be obtained as a converter product in the controlled catalytic oxidation of naphthalene vapors with air. The principle involved in the separation of the naphthoquinone is that of liquidliquid extraction. If a crude converter product of appropriate naphthalene content and suitable ratio of naphthoquinone to phthalic anhydride is dissolved in hot Water, the product liquetles and the phthalic anhydride is hydrated to phthalic acid. As a consequence, a four-component system, namely; water:phtha1ic acidznaphthoquinonernaphthalene results and two phases are formed; namely, an yaqueous layer containing the bulk of the phthalic acid and a naphthoquinone-naphthalene layer 'containing the bulk of the naphthoquinone.

To determine the complete quaternary phase diagram for the complex four-component system would be a major task and far beyond the requirements and needs of -a description of the present invention. Sufcient testing, and analyzing, however, has established that` naphthoquinone is highly soluble in the liquid naphthalene layer, whereas phthalic acid is negligibly soluble therein. Furthermore, the naphthoquinone is much lesspsoluble y in the hot water layer than is the phthalic acid. To state and vis .cumbersome and only moderately effective. Adv ditionaily, shortages in the supply ont .the solvent benzene have detracted from the dependability oi the process.

Another method involves the extraction .of .the mixture of naphthoquinone and phthalic acid or anhydride with an aqueous solution of an alkali, suchzas sodium carbonate,u fromV which the insoluble naphthoquinone lis separated by filtration in an impure form, which may be puriiied by ris-.crystallization from an organic solvent as a yellow-green product having Va melting point lof ,122 to 123 C. y

While extraction with aqueous alkalies, or equivalent materials, is potentially the cheapest and most convenient Vmethod for recovering naphthoquinone from mixtures also containing phthalic acid and/or anhydride, lthis, method, when applied, may cause deterioration of the naphthoquinone and does not produce a naphthoquinone in sufficiently pure form to bek acceptableV for s ome cornmercial purposes. f

One object, therefore, of the present invention is to provide an emcienta-nd inexpensive method for Ythe refcovery of naphthoquinone from mixtures containing phthalic anhydride and/or acid and naphthoquinone, l:which process does not involve expensive solvents `or re- 'quire the separation and recovery thereof.

' Another object of the present invention is to provide aV simple and economical process for recovering naphthoquinone in good yield and .qualityl from the vcrude converter product resulting from thecatalytic oxidation of naphthalene, which process vemploys materials inplentithis in terms of ratios, the results have indicated that the distribution ratio oi naphthoquinone between naphthalene and aqueous phthalic acid solution is high, whereas, conversely, the distribution ratio of phthalic acid between naphthalene and aqueous phthalic acid solution is low.

simple andrinexpensive matter and, consequently, two separate solutions may be obtained, one containing the bulk of the naphthoquinone and the other containing the phthalic acid. ln the case of the layer containing the naphthoquinone and the naphthalene, the separation of `the solvent naphthalene from the naphthoquinone, for example, by distillation or extraction processes, is

' I `relatively asimple matter, but may be omitted in the ,acid, the -phthalic acid may be recovered therefrom by event that the naphthoquinone is intended to be used in a process `in which the presence of naphthalene would not be objectionable, such as when naphthoquinone is reacted with butadiene in the preparation of anthraquinone.

In the icase of the aqueous layer containing the phthalic [crystallization upon cooling. If desired, the crystals may beleached, for example with chloroform, to-recover addil tional small amounts of naphthoquinone. The phthalic acid crystals may then be further processed as desired or required, such as, for example, by being dehydrated to recover phthalic anhydride. The mother liquor from which thephthalic acid crystals have been obtained may -be returned to the extraction process, or disposed of other- Wise, as desired.

The physical separation of these layers is relatively a the crude converter product, according to the principles of the present inventive concept, sutlicient water should be used to give a saturated or nearly saturated solution of aqueous phthalic acid at a temperature of from about 60 up to about 100 C. In the event that other amounts of water and other temperatures are used, the process becomes unsatisfactory for reasons to be described hereinafter.

When the `crude converter product is added to the hot water, it melts and becomes thoroughly dispersed by suflicient agitation or stirring. The naphthalene-naphthoquinone layer readily separates from the aqueous phthalic acid solution in a short time, and a physical division of the two layers may then be effected. The naphthalene-naphthoquinone layer is essentially free of water and analysis shows it to contain morey than about 40% to 60% naphthoquinone and less than 3 of phthalic acid.

The extraction results of several experimental runs are tabulated in Table `I.

sary if the naphthoquinone:naphthalene mol ratio in the oil layer is to be greater than 1:1, that is, 50 mol percent naphthoquinone. Temperatures much above 90 C., however, may not be desirable or practicable due to the increasing losses of naphthoquinone to the water layer as the temperature approaches 100 C., as well as to the greater possibility of decomposition of the naphthoquinone and the boiling of the water. Consequently, the preferred temperature of the present invention falls within the range of from about 75 C. to about 90 C.

With regard to the amount of water to be used in the dissolving of the crude converter mixture, it has been established that the loss of naphthoquinone to the water layer increases rapidly as the degree of saturation of the aqueous phthalic acid layer falls below 75%, at which point the percent loss is approximately 25%. Beyond that point and down to a saturation of 50%, whereat the loss is approximately 33% the process might be marginally commercially practicable. Below a saturation of 50%,

TABLE I Initial Wt. Ratios PA PA @Oog-1L (Hoi- 'PU cuide) 2. Y?? PAA lil. Nap.

E. Crude Phase NQ PA Final Wt. Ratios Apparent lstrib.

NQ Naph.

Percent Conc.

Percent Recov.

Percent Cone.

Pervent Recov.

oil in Bq Basis: Crude for rst four runs: 23.0% NQ; 20.0% nnphthalene (by difference); 48.0% PAA. (53.8% equivalent PA).

23.1% NQ; 18.2% naphthalene (by diferenoe); 58.7% PAA (65.8% equivalent PA).

Crude for last three runs With regard to the affect of temperature on the loss of naphthoquinone to the water layer, it has been established that `the loss is only slight or negligible within the `temperature range of from about 60 C. up to close to 100 C. On this basis, therefore, any Working ternperature in that range that is convenient operationally for the extraction process may be selected, depending upon the particular circumstances of the specific situation involved. However, within the principles of the the naphthoquinone loss increases sharply at a rate so great probably as to render the process economically impracticable. Consequently, within the principles of the present invention, any water usage within the range from saturation and saturation is acceptable, although the preferred range extends from about to 100% saturation.

The conclusions set forth in the preceding two paragraphs have been derived from the data tabulated in Table present invention, a temperature above 75 C. is neces- 5011 and Table Ill and illustrated in Figures l and 2.

TABLE 1I Water usage and NQ loss a! various temperatures for a specimen crude [Basis: lb. crude 60% PAA, i. e.. 67.3 lb. PA; 20% NQ; 20% naphthalene (by dtfference).l

'r mp irseei W 1b w W o s s L inermi? Lm' u 0 a B o, wln.- H 0 Pmper- No. 8l'- Nmper- No, No 100, r-

O. uration l Wn, lb. a cent cen cent 1b. pe

cent

1. 0 596 B63 10.15 0. 70 1.17 4. 75 24 90 0. 5 1, 259 1, 326 b. 08 0. 5l 0. 72 6. 80 34 0. 5, 237` 5, 304 1. 27 0.36 0. 41 18. l1 90 1. 0 775 842 8. 0 0. 55 0. R7 4. 63 Zi 80 0. 5 1, 617 1, 694 4. 0 0. 39 0. 55 6. 56 33 0. 125 6, 669 6, 736 1.0 0. 27 D. 31 18.16 01 1. 0 l, 203 1, 270 5. 3 0. 39 0. 59 4. 68 23 70 0. 5 2, 473 2. 540 2. 65 0 30 0. 40 6. 67 33 0.125 10. 093 10,16() 0. 67 0.18 0. 26 18. 59 93 1. 0 1. 858 925 3. 5 0. 27 0. 41 4. 77 24 60 0.5 3, 773 3. 850 1. 75 0. 19 0. 26 6. 84 34 0. 125 15, 333 15, 400 0. 44 0. 13 0.15 18. 20 D2 SNo=percent solubility oi naphthoquinone ln water alone O1 A=percent concentration of phthalitacid present Lnoxloss of naphthoquinone into the aqueous phase Wwlnweight oi the solu tion Srzqsnaphthslene solubility of naphthoquinone TABLE III Solubility of NQ and PA g./100 g. Solution (H20) Ratio: Alone Together Together] Alone Temp., G. 232g: Percent Percent T solubility sombuity S PA PAIN Q, PA/NQ NQ PA NQ PA N Q, PA

Table II, taken in conjunction with Figure 1, shows the of my invention, I consider the case not to be limited weight and percentage loss of naphthoquinone to the aqueous phthalic acid phase, as affected by the increasing amount of the water used and the consequent decreasing degree of saturation of the aqueous phthalic acid phase. The desirability of using operating conditions in which the degree of saturation of the aqueous phthalic acid is at least 50%, and preferably atleast 75% up to saturated conditions, is clear.

Table III shows the effect of varying temperatures on the solubility in water of naphthaquinone and phthalic acid, taken alone or together. The desirability of temperatures over 60 C. and up to 100 C., and preferably within the range 75 C. to 90 C., in View of the pertinent discussion and particularly Figure 2, is also clear.

Figure 2 sets forth the phase relations of naphthoquinone and naphthalene at varying temperatures and it is, of course, apparent in view of the preceding description that suicient naphthalene must be present in order to provide the necessary solvating action on the napthoquinone. When naphthoquinone is made by the catalytic oxidation of napthalene and the crude converter product is recovered as a solid containing essentially all of the products of the reaction, no diiiculties are normally encountered and the above-described processes proceed satisfactorily.

However, in some cases, the naphthalene concentration may not be suiiciently high to dissolve all of the naphthoquinone. For example, in the event that the hot converter gases coming from `the reactor are passed through recovery apparatus such as a warm, Wet absorber, the conditions therein may be suiiicient to carry oif large quantities of naphthalene. Consequently, in such a case the expelled naphthalene may be recovered and returned to the extraction process to provide the desired concentration of naphthalene. If desired, fresh naphthalene may be added, if such is found more convenient.

Although I have described but a few specic examples thereby nor to the specific substances and operating conditions mentioned therein, but to include various other equivalent compounds of similar constitution and other equivalent operating conditions as set forth in the claim appended hereto. It is understood that any suitable changes, modifications or variations may be made without departing from the spirit or scope ofthe inventive concept.

I claim:

A process for the recovery of naphthoquinone from a mixture of phthalic anhydride, naphthoquinone and naphthalene obtained by the controlled catalytic oxidation of napthalene vapors with air and containing about 48- by weight of phthalic anhydride and about 20-29% of unchanged naphthalene, the balance being substantially all naphthoquinone, which comprises admixing sucient water with said mixture at a temperature between about C. and 90 C. to convert the phthalic anhydride to plrthalic acid and to form an aqueous phthalic acid solution having a degree of saturation between about 75% and and thereby forming a two-layer system consisting of an aqueous layer containing most of the phthalic acid and a non-aqueous naphthoquinone-naphthalene layer containing most of the naphthoquinone, and separating said layers and recovering the naphrthoquinone from the nonaqueous layer.

References Cited in the le of this patent UNITED STATES PATENTS 1,284,888 Gibbs Nov. 12, 1918 1,285,117 Gibbs Nov. 19, 1918 2,190,001 Talbert Feb. 13, 1940 2,536,833 Bailey Jan. 2, 1951 OTHER REFERENCES Marek & Hahn, Catalytic Oxidation of Organic Compounds in the Vapor Phase, 1932, p. 408. 

